In human diabetes mellitus certain vascular changes are causally related to morbidity and mortality, and are a quantitative indicator of disease development and potential means for evaluating therapy. To date, the only satisfactory animal model for the study of diabetic microangiopathy has been the metasomatotrophin of Alloxan diabetic dog, which must be diabetic for nearly five years before showing characteristic capillary basement membrane changes. Spontaneous diabetes mellitus was found in the colony of Mystromys albicaudatus (South African hamster) at the University of Missouri. This disease has been characterized with regard to glucose and insulin metabolism and mode of inheritance, and recent studies have demonstrated light microscopic changes in the renal glomerulus similar to intercapillary glomerulosclerosis in human diabetics. In addition, we have E.M. evidence of diabetic microangiopathy in skeletal muscle. This colony is the only short-lived, spontanously diabetic animal model that exhibits diabetic microangiopathy in skeletal muscle. Studies of this strain of mystromys during five years indicates it to be a highly useful and much less expensive model for the study of human diabetes, but certain questions remain to be answered before the the model is ready for general use. This project is directed toward answering these questions: 1. How are the capillary basement membrane (c.b.m.) changes related to the severity and duration of diabetes? 2. How are the c.b.m. changes related to animals' age and sex? 3. Can the c.b.m. changes be related to glomerular capillary basement membrane changes? 4. How do the c.b.m. changes of diabetic mystromys compare with those of diabetic human beings?